The invention relates to a clutch device for a motor vehicle.
The well-known clutch devices, from which the invention proceeds, are known in many variations in the state of the art. In addition to the actual clutch, other elements are connected to a combustion engine by a drive shaft on the drive end and are connected to a transmission by an output shaft on the output-end. For example, the drive shaft is connected to the output shaft when the clutch is put into motion. Such clutch devices include an operating device for moving this clutch.
The invention relates to clutch devices in which the operating device comprises a pressure piston. This pressure piston is arranged in a housing in accordance with the state of the art. This pressure piston is furthermore movably guided within this housing. An appropriate sliding movement by the pressure piston can move the clutch.
In order for the pressure piston to generate such a sliding movement, it is necessary to generate a corresponding pressure force. This is normally done hydraulically. To be specific, the housing and pressure piston according to the state of the art are arranged together in such a manner that they enclose a hollow space, hereinafter called a pressure chamber, which can be pressurized with a suitable pressurizing agent, usually a synthetic oil designed for this purpose, in order to generate the aforementioned pressure force.
After a clutch has been put into motion, it is necessary to return the pressure piston back to its starting position. It is desirable to selectively meter the pressure force that causes the sliding movement of the piston. Control of the pressure force is consequently necessary if the housing and pressure piston represent parts that rotate with the drive shaft. In this case, the pressure of the pressurizing agent within the aforementioned pressure chamber will rise with the speed of the rotary motion, a result which is generally undesirable.
To be able to return the pressure piston back to its starting position and additionally be able to control the pressure force that causes the sliding movement of the piston, the operating device in accordance with the state of the art comprises a mechanism for generating a counterpressure force that operates against the aforementioned pressure force. A mechanism of this type for generating the counterpressure comprises another piston, which will hereinafter be called a balance piston. This balance piston is so arranged that it, together with the pressure piston and housing, encloses a hollow space, which will hereinafter be called a balance chamber. Like the aforementioned pressure chamber, this balance chamber can be pressurized with a (counter) pressurizing agent, preferably a synthetic oil, to generate the counterpressure.
To generate the counterpressure operating on the pressure piston, it is necessary to hold the balance piston immobile relative to the housing when the balance chamber is pressurized with the (counter) pressurizing agent. Mechanisms for this purpose that are known from the state of the art require additional space within the clutch device and are also relatively expensive to manufacture and/or take more time to assemble, which is likewise reflected in a higher price for the end product.
To explain the facts, which have been depicted very generally above, the problematic nature shall now again be presented by way of example based on a multi-disc clutch device in accordance with the state of the art illustrated in FIG. 4.
The illustrated multi-disc clutch device comprises a housing designed essentially rotationally symmetrical to an axis 0x and connected to a drive shaft (unillustrated) on the drive end 22 and consisting of an essentially hollow cylindrical external plate-disc carrier 5 and an essentially hollow cylindrical center section 15.4 coaxial to the essentially hollow cylindrical external plate-disc carrier 5 and located therein. A constituent part of the multi-disc clutch device is furthermore an internal plate-disc carrier 7 on the output end 23 connected to an output shaft (not illustrated) and designed essentially rotationally symmetrical to the axis 0x. 
As can be deduced from the drawing, external and internal plate-disc carriers 5, 7 are carriers of so-called external and internal plate-discs 6, 8. These are mounted on their respective external and internal plate-disc carriers 5, 7 basically tight yet with a limited axial movement. The entire fitting arrangement, in the present case consisting of three external and three internal plate-discs 5, 7 is called a disc pack 4. External and internal plate-discs 5, 7 mesh together comb-like and can be brought together into frictional connection in pairs. The disc-plate that terminates the disc pack 4 on one end and whose axial movement is restricted on one end by means of a locking ring 27 (here an external plate-disc) is called an end plate. In FIG. 4, this has been assigned the reference character 9. The disc-plate that terminates the other end of disc pack 4 (presently an internal plate-disc) is called a pressure plate. In FIG. 4, this pressure plate has been assigned reference character 10.
This fitting arrangement of a disc pack 4 consisting of several plate-discs (six in the present case) on external and internal plate-disc carriers 5, 7, preferably being cooled for example by a coolant like cooling oil 26 supplied via a cooling oil chamber 13, forms the portion of a multi-disc clutch device called “actual clutch”.
Another constituent part of the multi-disc clutch device in accordance with the state of the art and depicted in FIG. 4 is the previously mentioned operating device for moving this clutch. As likewise explained in detail above, this operating device comprises of the pressure piston 1 and the balance piston 2.
Pressure piston 1 is designed essentially circular. The piston's inside wall is guided to slide on the outside wall of the center section 15.4, which is basically shaped like a cylinder jacket. By an appropriate sliding movement, pressure piston 1 presses against the pressure plate 10 of disc pack 4 by means of an appropriate pressure element 14, which is designed circular in the present case, so that the disc pack 4 is pressed together, end plate 9 having no means of axial evasion, and the separate neighboring disc-plates 6, 8 form a frictional connection, thus moving the clutch.
The housing and pressure piston 1 fit together forming a hollow space. This hollow space, the so-called pressure chamber, which is presently sealed against its surroundings by two sealing rings 20, 21, is labeled with the reference character 11 in the Figure.
Pressure oil 24 can be added to this pressure chamber 11 through one or more holes in center section 15.4 that run radially. The corresponding holes are consequently called pressure oil channels. One of these pressure oil channels can be found in FIG. 4, where it is labeled with reference character 17.
In the exemplary embodiment depicted in FIG. 4, balance piston 2, named above as a constituent part of the operating device, is designed essentially circular. It is so arranged that it, in combination with the pressure piston 1 and center section 15.4 of the housing, encloses a hollow space. This hollow space is called a balance chamber and is assigned reference character 12 in FIG. 4.
Like pressure chamber 11 described above, balance chamber 12 can be pressurized with a (counter) pressurizing agent, hereinafter called compensating oil 25, which is added through appropriate holes in order to generate the aforementioned counterpressure force. The holes for adding compensating oil 25 will hereinafter be called compensating oil channels. FIG. 4 depicts one of these compensating oil channels radially penetrating through the center section 15.4 of the housing. It is labeled with reference character 18.4.
In the presented exemplary embodiment in accordance with the state of the art, a spring assembly 3, which is supported by an inside wall of the balance piston 2 and held in opposition to the sliding direction of pressure piston 1 when the clutch is put into motion against pressure piston 1, is arranged in balance chamber 12 to further increase the counterpressure force to be generated.
For the sliding of piston 1 in an axial direction to be able to generate an appropriate counterpressure in balance chamber 12 at all when the clutch is put into motion, it is necessary both to seal the balance chamber 12 against its surroundings and also to hold balance piston 2 at least axially immobile. The first of these functions is accomplished with a circular sealing lip 19 that seals the adjacent walls of pressure piston 1 and balance piston 2. The axial slide protection is usually accomplished with a locking ring 16.4 in accordance with the state of the art.
Although this fitting arrangement has been proven in principle, there still exists the need to present an inexpensive and space-saving alternative solution.
It is consequently the objective of the invention to elaborate and develop the known clutch devices in such a manner that they will cost less to manufacture and also feature smaller dimensions.
This task is solved according to invention by a generic clutch device with the characteristics of the characterizing portion of claim 1.
Advantageous embodiments and further developments of the invention are given in the dependent claims.
The essential idea of the invention consists of providing a latching or catching mechanism to basically hold the balance piston immobile to the housing when the clutch is put into motion. It is rapid and easy to assemble a balance piston using this type of latching or catching mechanism. In addition, latching or catching mechanisms are known from many other applications, ensuring inexpensive manufacture and space-saving design.
An advantageous variant of the invention consists of the latching or catching mechanism, hereinafter only called latching mechanism for the sake of simplicity, comprising at least one latching element of a first kind, which is assigned to the housing, and at least one latching element of a second kind, which is assigned to the balance piston, the latching elements of the first and second kind being brought into latching or catching engagement with each other. This variant represents the simplest form of a latch or catch lock and is therefore to be preferred over complicated twist-catch or screw-catch mechanisms, which are of course also conceivable.
In a special embodiment of this variant, the invention provides for the latching element of the second kind to be a constituent part of the balance piston. In some cases it is also advantageous, however, for the latching element of the second kind to be a constituent part of a separate balance-piston holding device, possibly specially provided for this. Both variants can also be applied in combination, if necessary.
A solution to the presented task is provided in any case.
For the cases in which the housing is designed essentially rotationally symmetrical to an axis and comprises of a center section, essentially shaped like a cylinder jacket, whose outside wall guides the inside wall of the pressure piston, which is designed essentially circular, so that the pressure piston slides axially, and on which center section the balance piston is held immobile when the clutch is put into motion in the axial sliding direction of the pressure piston, the balance piston likewise being designed circular, such cases including particularly such a multi-disc clutch device in accordance with the state of the art as illustrated in FIG. 4, it is provided according to invention that the latching element of the first kind is a groove essentially revolving coaxially in the inside wall or outside wall of the center section, and the latching element of the second kind comprises of at least one latching clip or detent that can engage the revolving groove for locking.
The at least one latching clip or detent is preferably formed on the end of a finger essentially axially separated from the balance piston or from the balance-piston holding device. A large number of these latching clips attached on the end of a finger are usually attached coaxial to a circular end of the balance piston or balance-piston holding device. Alternatively, it is also provided according to invention that a single latching clip is designed revolving coaxially.
In another embodiment of the invention it is moreover provided that the balance-piston holding device, which is preferably circular, is designed to fit a balance piston similar to that of FIG. 4.
Three exemplary embodiments of the invention are illustrated in the drawings and compared to one variant of a multi-disc clutch device according to the state of the art.
The exemplary embodiments of the invention will be explained in more detail in the following.